The Perfect Job - error when clicking for job details

The Perfect Job (part 1) was written in June 28, 2001 and I have a problem with it. After having spent quite some time searching for the original discussion threads on it I conclude they don't exist anymore.

You guys are very clever and I've found hundreds of answers on this site, but this one eludes me.

When I click on a job (ie 'Senior Web Developer (X5436)') within the job_list.php page I've set up I get sent to the error page which I believe is defined by the code at the top of the page it's trying to interact with (job_details.php):